Fecal Bacteroidales Diversity and Decay in Response to Variations in Temperature and Salinity

The ideal host-associated genetic fecal marker would be capable of predicting the presence of specific pathogens of concern. Flowthrough freshwater microcosms containing mixed feces and inocula of the pathogens Campylobacter jejuni, Salmonella enterica serovar Typhimurium, and adenovirus were placed at ambient temperature in the presence and absence of diurnal sunlight. The total Enterococcus DNA increased during the early periods (23 h) under sunlight exposure, even though cultivable Enterococcus and DNA in intact cells, as measured by propidium monoazide (PMA), decreased with first-order kinetics during the entire period. We found a significant difference in the decay of host-associated Bacteroidales cells between sunlight exposure and dark conditions (P value < 0.05), whereas the persistence of host-associated Bacteroidales DNA was comparable. The 2-log reduction times of adenovirus were 72 h for sunlight exposure and 99 h for dark conditions with similar decay rate constants (P value ‫؍‬ 0.13). The persistences of fecal Bacteroidales cells and Campylobacter cells exposed to sunlight were similar, and hostassociated Bacteroidales DNA and waterborne pathogen DNA were degraded at comparable rates (P values > 0.05). Overall, the ratio of quantitative PCR (qPCR) cycle threshold (C T ) values with and without PMA treatment was indicative of the time elapsed since inoculation of the microcosm with (i) fecal material from different animal sources based on host-associated Bacteroidales and (ii) pure cultures of bacterial pathogens. The use of both PMA-qPCR and qPCR may yield more realistic information about recent sources of fecal contamination and result in improved prediction of waterborne pathogens and assessment of health risk.

Section: Discussionmentioning

confidence: 99%

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confidence: 96%

Survival of Host-Associated Bacteroidales Cells and Their Relationship with Enterococcus spp., Campylobacter jejuni, Salmonella enterica Serovar Typhimurium, and Adenovirus in Freshwater Microcosms as Measured by Propidium Monoazide-Quantitative PCR

Bae

Wuertz

2012

“…Temperature has also been shown to correlate strongly with inactivation of Bacteroidales spp. in water microcosms (19)(20)(21)(22)(23). Positive correlations between moisture and FIB concentrations have been documented in several studies (12,(24)(25)(26)(27), but an overall negative relationship between moisture and Escherichia coli (14) has been reported.…”

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confidence: 99%

Decay of Fecal Indicator Bacterial Populations and Bovine-Associated Source-Tracking Markers in Freshly Deposited Cow Pats

Oladeinde

Bohrmann

Wong

et al. 2014

Understanding the survival of fecal indicator bacteria (FIB) and microbial source-tracking (MST) markers is critical to developing pathogen fate and transport models. Although pathogen survival in water microcosms and manure-amended soils is well documented, little is known about their survival in intact cow pats deposited on pastures. We conducted a study to determine decay rates of fecal indicator bacteria (Escherichia coli and enterococci) and bovine-associated MST markers (CowM3, Rum-2-bac, and GenBac) in 18 freshly deposited cattle feces from three farms in northern Georgia. Samples were randomly assigned to shaded or unshaded treatment in order to determine the effects of sunlight, moisture, and temperature on decay rates. A general linear model (GLM) framework was used to determine decay rates. Shading significantly decreased the decay rate of the E. coli population (P < 0.0001), with a rate of ؊0.176 day ؊1 for the shaded treatment and ؊0.297 day ؊1 for the unshaded treatment. Shading had no significant effect on decay rates of enterococci, CowM3, Rum-2-bac, and GenBac (P > 0.05). In addition, E. coli populations showed a significant growth rate (0.881 day ؊1 ) in the unshaded samples during the first 5 days after deposition. UV-B was the most important parameter explaining the decay rate of E. coli populations. A comparison of the decay behaviors among all markers indicated that enterococcus concentrations exhibit a better correlation with the MST markers than E. coli concentrations. Our results indicate that bovine-associated MST markers can survive in cow pats for at least 1 month after excretion, and although their decay dynamic differs from the decay dynamic of E. coli populations, they seem to be reliable markers to use in combination with enterococci to monitor fecal pollution from pasture lands. E levated levels of fecal indicator bacteria (FIB) remain the most common cause of impairment in streams and rivers in the United States, with agriculture as the primary source of contamination (1). The federal Clean Water Act defines impaired surface waters as rivers, lakes, or streams that do not meet one or more water quality standards and therefore categorizes these water resources as too polluted for their intended uses. FIB are recommended for water monitoring because of their correlation with gastrointestinal illness (2-4), but they cannot indicate the origin of fecal pollution. This shortcoming is one of the challenges present when attempting to protect and remediate water sources that are impaired due to fecal contamination (5). Emerging libraryand culture-independent microbial source-tracking (MST) methods that target host-associated markers and offer information about the sources of fecal contamination are now used widely by state and federal agencies monitoring water resources (6-9). Information can be used for total maximum daily load (TMDL) development and implementation of remediation practices.Ideally, MST markers and FIB will have similar fates and transport behaviors governed by their co...

“…It has been suggested that qPCR methods can be used to allocate fecal contributions from various hosts to degraded water quality by comparing the relative abundances of different host-specific Bacteroides markers and the total Bacteroidales abundance (17,18). For accurate source apportionment to occur, one needs to understand both the abundance of Bacteroides bacteria in host feces and the survival of these host-specific microbial markers after deposition in the environment.…”

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confidence: 99%

“…As such, many studies were undertaken recently to assess persistence and decay of host-specific Bacteroides markers in freshwater (13,(19)(20)(21)(22)(23), marine waters (11,12,17,24,25), manure-amended soils (26,27), and animal feces (9), under a variety of conditions. In general, studies have reported a positive relationship between Bacteroidales decay rates and temperature (17,20), a negative relationship between salinity and decay rates (17,25), and a variable relationship between decay rates and the presence or absence of light (13,28). Given that Bacteroidales is a deeply divergent order based on 16S rRNA gene phylogeny, it is not surprising that different Bacteroidales clades may have differing environmental persistences after leaving the intestines of warm-blooded animals in fecal material.…”

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confidence: 99%

Evidence for Extraintestinal Growth of Bacteroidales Originating from Poultry Litter

Weidhaas

Mantha

Hair

et al. 2015

bWater quality monitoring techniques that target microorganisms in the order Bacteroidales are potential alternatives to conventional methods for detection of fecal indicator bacteria. Bacteroidales and members of the genus Bacteroides have been the focus of microbial source tracking (MST) investigations for discriminating sources of fecal pollution (e.g., human or cattle feces) in environmental waters. For accurate source apportionment to occur, one needs to understand both the abundance of Bacteroides in host feces and the survival of these host-associated microbial markers after deposition in the environment. Studies were undertaken to evaluate the abundance, persistence, and potential for growth of Bacteroidales originating from poultry litter under oxic and anoxic environmental conditions. Bacteroidales abundance, as determined by quantitative PCR (qPCR) with GenBac primers and probe, increased 2 to 5 log gene copies ml ؊1 and 2 log gene copies g litter ؊1 under most conditions during incubation of poultry litter in a variety of laboratory microcosm and field mesocosm studies. DNA sequencing of the Bacteroidales organisms in the litter identified taxa with sequences corresponding exactly to the GenBac primer and probe sequences and that were closely related to Bacteroides uniformis, B. ovatus, and B. vulgatus. These results suggest that MST studies using qPCR methods targeting Bacteroidales in watersheds that are affected by poultry litter should be interpreted cautiously. Growth of Bacteroidales originating from poultry litter in environmental waters may occur while Bacteroidales growth from other fecal sources declines, thus confounding the interpretation of MST results.